<style>
    .item1{background: LightSkyBlue;}

    .item2 {
        background: LightSalmon;
        /* 请在本行以下添加你的代码 */
        justify-self: center;

        /* 请在本行以上添加你的代码 */
    }

    .item3{background:PaleTurquoise;}
    .item4{background:LightPink;}
    .item5{background:PaleGreen;}

    .container {
        font-size: 40px;
        min-height: 300px;
        width: 100%;
        background: LightGray;
        display: grid;
        grid-template-columns: 1fr 1fr 1fr;
        grid-template-rows: 1fr 1fr 1fr;
        grid-gap: 10px;
    }
</style>

<div class="container">
    <div class="item1">1</div>
    <div class="item2">2</div>
    <div class="item3">3</div>
    <div class="item4">4</div>
    <div class="item5">5</div>
</div>